Tag Archives: silicon

New semiconductor material from pigment produced by fungi?

Chlorociboria Aeruginascens fungus on a tree log. (Image: Oregon State University)

Apparently the pigment derived from the fungi you see in the above picture is used by visual artists and, perhaps soon, will be used by electronics manufacturers. From a June 5, 2018 news item on Nanowerk,

Researchers at Oregon State University are looking at a highly durable organic pigment, used by humans in artwork for hundreds of years, as a promising possibility as a semiconductor material.

Findings suggest it could become a sustainable, low-cost, easily fabricated alternative to silicon in electronic or optoelectronic applications where the high-performance capabilities of silicon aren’t required.

Optoelectronics is technology working with the combined use of light and electronics, such as solar cells, and the pigment being studied is xylindein.

A June 5, 2018 Oregon State University news release by Steve Lundeberg, which originated the news item, expands on the theme,

“Xylindein is pretty, but can it also be useful? How much can we squeeze out of it?” said Oregon State University [OSU] physicist Oksana Ostroverkhova. “It functions as an electronic material but not a great one, but there’s optimism we can make it better.”

Xylindien is secreted by two wood-eating fungi in the Chlorociboria genus. Any wood that’s infected by the fungi is stained a blue-green color, and artisans have prized xylindein-affected wood for centuries.

The pigment is so stable that decorative products made half a millennium ago still exhibit its distinctive hue. It holds up against prolonged exposure to heat, ultraviolet light and electrical stress.

“If we can learn the secret for why those fungi-produced pigments are so stable, we could solve a problem that exists with organic electronics,” Ostroverkhova said. “Also, many organic electronic materials are too expensive to produce, so we’re looking to do something inexpensively in an ecologically friendly way that’s good for the economy.”

With current fabrication techniques, xylindein tends to form non-uniform films with a porous, irregular, “rocky” structure.

“There’s a lot of performance variation,” she said. “You can tinker with it in the lab, but you can’t really make a technologically relevant device out of it on a large scale. But we found a way to make it more easily processed and to get a decent film quality.”

Ostroverkhova and collaborators in OSU’s colleges of Science and Forestry blended xylindein with a transparent, non-conductive polymer, poly(methyl methacrylate), abbreviated to PMMA and sometimes known as acrylic glass. They drop-cast solutions both of pristine xylindein and a xlyindein-PMMA blend onto electrodes on a glass substrate for testing.

They found the non-conducting polymer greatly improved the film structure without a detrimental effect on xylindein’s electrical properties. And the blended films actually showed better photosensitivity.

“Exactly why that happened, and its potential value in solar cells, is something we’ll be investigating in future research,” Ostroverkhova said. “We’ll also look into replacing the polymer with a natural product – something sustainable made from cellulose. We could grow the pigment from the cellulose and be able to make a device that’s all ready to go.

“Xylindein will never beat silicon, but for many applications, it doesn’t need to beat silicon,” she said. “It could work well for depositing onto large, flexible substrates, like for making wearable electronics.”

This research, whose findings were recently published in MRS Advances, represents the first use of a fungus-produced material in a thin-film electrical device.

“And there are a lot more of the materials,” Ostroverkhova said. “This is just first one we’ve explored. It could be the beginning of a whole new class of organic electronic materials.”

Here’s a link to and a citation for the paper,

Fungi-Derived Pigments for Sustainable Organic (Opto)Electronics by Gregory Giesbers, Jonathan Van Schenck, Sarath Vega Gutierrez, Sara Robinson. MRS Advances https://doi.org/10.1557/adv.2018.446 Published online: 21 May 2018

This paper is behind a paywall.

Yes! Art, genetic modifications, gene editing, and xenotransplantation at the Vancouver Biennale (Canada)

Patricia Piccinini’s Curious Imaginings Courtesy: Vancouver Biennale [downloaded from http://dailyhive.com/vancouver/vancouver-biennale-unsual-public-art-2018/]

Up to this point, I’ve been a little jealous of the Art/Sci Salon’s (Toronto, Canada) January 2018 workshops for artists and discussions about CRISPR ((clustered regularly interspaced short palindromic repeats))/Cas9 and its social implications. (See my January 10, 2018 posting for more about the events.) Now, it seems Vancouver may be in line for its ‘own’ discussion about CRISPR and the implications of gene editing. The image you saw (above) represents one of the installations being hosted by the 2018 – 2020 edition of the Vancouver Biennale.

While this posting is mostly about the Biennale and Piccinini’s work, there is a ‘science’ subsection featuring the science of CRISPR and xenotransplantation. Getting back to the Biennale and Piccinini: A major public art event since 1988, the Vancouver Biennale has hosted over 91 outdoor sculptures and new media works by more than 78 participating artists from over 25 countries and from 4 continents.

Quickie description of the 2018 – 2020 Vancouver Biennale

The latest edition of the Vancouver Biennale was featured in a June 6, 2018 news item on the Daily Hive (Vancouver),

The Vancouver Biennale will be bringing new —and unusual— works of public art to the city beginning this June.

The theme for this season’s Vancouver Biennale exhibition is “re-IMAGE-n” and it kicks off on June 20 [2018] in Vanier Park with Saudi artist Ajlan Gharem’s Paradise Has Many Gates.

Gharem’s architectural chain-link sculpture resembles a traditional mosque, the piece is meant to challenge the notions of religious orthodoxy and encourages individuals to image a space free of Islamophobia.

Melbourne artist Patricia Piccinini’s Curious Imaginings is expected to be one of the most talked about installations of the exhibit. Her style of “oddly captivating, somewhat grotesque, human-animal hybrid creature” is meant to be shocking and thought-provoking.

Piccinini’s interactive [emphasis mine] experience will “challenge us to explore the social impacts of emerging biotechnology and our ethical limits in an age where genetic engineering and digital technologies are already pushing the boundaries of humanity.”

Piccinini’s work will be displayed in the 105-year-old Patricia Hotel in Vancouver’s Strathcona neighbourhood. The 90-day ticketed exhibition [emphasis mine] is scheduled to open this September [2018].

Given that this blog is focused on nanotechnology and other emerging technologies such as CRISPR, I’m focusing on Piccinini’s work and its art/science or sci-art status. This image from the GOMA Gallery where Piccinini’s ‘Curious Affection‘ installation is being shown from March 24 – Aug. 5, 2018 in Brisbane, Queensland, Australia may give you some sense of what one of her installations is like,

Courtesy: Queensland Art Gallery | Gallery of Modern Art (QAGOMA)

I spoke with Serena at the Vancouver Biennale office and asked about the ‘interactive’ aspect of Piccinini’s installation. She suggested the term ‘immersive’ as an alternative. In other words, you won’t be playing with the sculptures or pressing buttons and interacting with computer screens or robots. She also noted that the ticket prices have not been set yet and they are currently developing events focused on the issues raised by the installation. She knew that 2018 is the 200th anniversary of the publication of Mary Shelley’s Frankenstein but I’m not sure how the Biennale folks plan (or don’t plan)  to integrate any recognition of the novle’s impact on the discussions about ‘new’ technologies .They expect Piccinini will visit Vancouver. (Note 1: Piccinini’s work can  also be seen in a group exhibition titled: Frankenstein’s Birthday Party at the Hosfselt Gallery in San Francisco (California, US) from June 23 – August 11, 2018.  Note 2: I featured a number of international events commemorating the 200th anniversary of the publication of Mary Shelley’s novel, Frankenstein, in my Feb. 26, 2018 posting. Note 3: The term ‘Frankenfoods’ helped to shape the discussion of genetically modified organisms and food supply on this planet. It was a wildly successful campaign for activists affecting legislation in some areas of research. Scientists have not been as enthusiastic about the effects. My January 15, 2009 posting briefly traces a history of the term.)

The 2018 – 2020 Vancouver Biennale and science

A June 7, 2018 Vancouver Biennale news release provides more detail about the current series of exhibitions,

The Biennale is also committed to presenting artwork at the cutting edge of discussion and in keeping with the STEAM (science, technology, engineering, arts, math[ematics]) approach to integrating the arts and sciences. In August [2018], Colombian/American visual artist Jessica Angel will present her monumental installation Dogethereum Bridge at Hinge Park in Olympic Village. Inspired by blockchain technology, the artwork’s design was created through the integration of scientific algorithms, new developments in technology, and the arts. This installation, which will serve as an immersive space and collaborative hub for artists and technologists, will host a series of activations with blockchain as the inspirational jumping-off point.

In what is expected to become one of North America’s most talked-about exhibitions of the year, Melbourne artist Patricia Piccinini’s Curious Imaginings will see the intersection of art, science, and ethics. For the first time in the Biennale’s fifteen years of creating transformative experiences, and in keeping with the 2018-2020 theme of “re-IMAGE-n,” the Biennale will explore art in unexpected places by exhibiting in unconventional interior spaces.  The hyperrealist “world of oddly captivating, somewhat grotesque, human-animal hybrid creatures” will be the artist’s first exhibit in a non-museum setting, transforming a wing of the 105-year-old Patricia Hotel. Situated in Vancouver’s oldest neighbourbood of Strathcona, Piccinini’s interactive experience will “challenge us to explore the social impacts of emerging bio-technology and our ethical limits in an age where genetic engineering and digital technologies are already pushing the boundaries of humanity.” In this intimate hotel setting located in a neighborhood continually undergoing its own change, Curious Imaginings will empower visitors to personally consider questions posed by the exhibition, including the promises and consequences of genetic research and human interference. …

There are other pieces being presented at the Biennale but my special interest is in the art/sci pieces and, at this point, CRISPR.

Piccinini in more depth

You can find out more about Patricia Piccinini in her biography on the Vancouver Biennale website but I found this Char Larsson April 7, 2018 article for the Independent (UK) more informative (Note: A link has been removed),

Patricia Piccinini’s sculptures are deeply disquieting. Walking through Curious Affection, her new solo exhibition at Brisbane’s Gallery of Modern Art, is akin to entering a science laboratory full of DNA experiments. Made from silicone, fibreglass and even human hair, her sculptures are breathtakingly lifelike, however, we can’t be sure what life they are like. The artist creates an exuberant parallel universe where transgenic experiments flourish and human evolution has given way to genetic engineering and DNA splicing.

Curious Affection is a timely and welcome recognition of Piccinini’s enormous contribution to reaching back to the mid-1990s. Working across a variety of mediums including photography, video and drawing, she is perhaps best known for her hyperreal creations.

As a genre, hyperrealism depends on the skill of the artist to create the illusion of reality. To be truly successful, it must convince the spectator of its realness. Piccinini acknowledges this demand, but with a delightful twist. The excruciating attention to detail deliberately solicits our desire to look, only to generate unease, as her sculptures are imbued with a fascinating otherness. Part human, part animal, the works are uncannily familiar, but also alarmingly “other”.

Inspired by advances in genetically modified pigs to generate replacement organs for humans [also known as xenotransplantation], we are reminded that Piccinini has always been at the forefront of debates concerning the possibilities of science, technology and DNA cloning. She does so, however, with a warm affection and sense of humour, eschewing the hysterical anxiety frequently accompanying these scientific developments.

Beyond the astonishing level of detail achieved by working with silicon and fibreglass, there is an ethics at work here. Piccinini is asking us not to avert our gaze from the other, and in doing so, to develop empathy and understanding through the encounter.

I encourage anyone who’s interested to read Larsson’s entire piece (April 7, 2018 article).

According to her Wikipedia entry, Piccinini works in a variety of media including video, sound, sculpture, and more. She also has her own website.

Gene editing and xenotransplantation

Sarah Zhang’s June 8, 2018 article for The Atlantic provides a peek at the extraordinary degree of interest and competition in the field of gene editing and CRISPR ((clustered regularly interspaced short palindromic repeats))/Cas9 research (Note: A link has been removed),

China Is Genetically Engineering Monkeys With Brain Disorders

Guoping Feng applied to college the first year that Chinese universities reopened after the Cultural Revolution. It was 1977, and more than a decade’s worth of students—5.7 million—sat for the entrance exams. Feng was the only one in his high school to get in. He was assigned—by chance, essentially—to medical school. Like most of his contemporaries with scientific ambitions, he soon set his sights on graduate studies in the United States. “China was really like 30 to 50 years behind,” he says. “There was no way to do cutting-edge research.” So in 1989, he left for Buffalo, New York, where for the first time he saw snow piled several feet high. He completed his Ph.D. in genetics at the State University of New York at Buffalo.

Feng is short and slim, with a monk-like placidity and a quick smile, and he now holds an endowed chair in neuroscience at MIT, where he focuses on the genetics of brain disorders. His 45-person lab is part of the McGovern Institute for Brain Research, which was established in 2000 with the promise of a $350 million donation, the largest ever received by the university. In short, his lab does not lack for much.

Yet Feng now travels to China several times a year, because there, he can pursue research he has not yet been able to carry out in the United States. [emphasis mine] …

Feng had organized a symposium at SIAT [Shenzhen Institutes of Advanced Technology], and he was not the only scientist who traveled all the way from the United States to attend: He invited several colleagues as symposium speakers, including a fellow MIT neuroscientist interested in tree shrews, a tiny mammal related to primates and native to southern China, and Chinese-born neuroscientists who study addiction at the University of Pittsburgh and SUNY Upstate Medical University. Like Feng, they had left China in the ’80s and ’90s, part of a wave of young scientists in search of better opportunities abroad. Also like Feng, they were back in China to pursue a type of cutting-edge research too expensive and too impractical—and maybe too ethically sensitive—in the United States.

Here’s what precipitated Feng’s work in China, (from Zhang’s article; Note: Links have been removed)

At MIT, Feng’s lab worked on genetically engineering a monkey species called marmosets, which are very small and genuinely bizarre-looking. They are cheaper to keep due to their size, but they are a relatively new lab animal, and they can be difficult to train on lab tasks. For this reason, Feng also wanted to study Shank3 on macaques in China. Scientists have been cataloging the social behavior of macaques for decades, making it an obvious model for studies of disorders like autism that have a strong social component. Macaques are also more closely related to humans than marmosets, making their brains a better stand-in for those of humans.

The process of genetically engineering a macaque is not trivial, even with the advanced tools of CRISPR. Researchers begin by dosing female monkeys with the same hormones used in human in vitro fertilization. They then collect and fertilize the eggs, and inject the resulting embryos with CRISPR proteins using a long, thin glass needle. Monkey embryos are far more sensitive than mice embryos, and can be affected by small changes in the pH of the injection or the concentration of CRISPR proteins. Only some of the embryos will have the desired mutation, and only some will survive once implanted in surrogate mothers. It takes dozens of eggs to get to just one live monkey, so making even a few knockout monkeys required the support of a large breeding colony.

The first Shank3 macaque was born in 2015. Four more soon followed, bringing the total to five.

To visit his research animals, Feng now has to fly 8,000 miles across 12 time zones. It would be a lot more convenient to carry out his macaque research in the United States, of course, but so far, he has not been able to.

He originally inquired about making Shank3 macaques at the New England Primate Research Center, one of eight national primate research centers then funded by the National Institutes of Health in partnership with a local institution (Harvard Medical School, in this case). The center was conveniently located in Southborough, Massachusetts, just 20 miles west of the MIT campus. But in 2013, Harvard decided to shutter the center.

The decision came as a shock to the research community, and it was widely interpreted as a sign of waning interest in primate research in the United States. While the national primate centers have been important hubs of research on HIV, Zika, Ebola, and other diseases, they have also come under intense public scrutiny. Animal-rights groups like the Humane Society of the United States have sent investigators to work undercover in the labs, and the media has reported on monkey deaths in grisly detail. Harvard officially made its decision to close for “financial” reasons. But the announcement also came after the high-profile deaths of four monkeys from improper handling between 2010 and 2012. The deaths sparked a backlash; demonstrators showed up at the gates. The university gave itself two years to wind down their primate work, officially closing the center in 2015.

“They screwed themselves,” Michael Halassa, the MIT neuroscientist who spoke at Feng’s symposium, told me in Shenzhen. Wei-Dong Yao, another one of the speakers, chimed in, noting that just two years later CRISPR has created a new wave of interest in primate research. Yao was one of the researchers at Harvard’s primate center before it closed; he now runs a lab at SUNY Upstate Medical University that uses genetically engineered mouse and human stem cells, and he had come to Shenzhen to talk about restarting his addiction research on primates.

Here’s comes the competition (from Zhang’s article; Note: Links have been removed),

While the U.S. government’s biomedical research budget has been largely flat, both national and local governments in China are eager to raise their international scientific profiles, and they are shoveling money into research. A long-rumored, government-sponsored China Brain Project is supposed to give neuroscience research, and primate models in particular, a big funding boost. Chinese scientists may command larger salaries, too: Thanks to funding from the Shenzhen local government, a new principal investigator returning from overseas can get 3 million yuan—almost half a million U.S. dollars—over his or her first five years. China is even finding success in attracting foreign researchers from top U.S. institutions like Yale.

In the past few years, China has seen a miniature explosion of genetic engineering in monkeys. In Kunming, Shanghai, and Guangzhou, scientists have created monkeys engineered to show signs of Parkinson’s, Duchenne muscular dystrophy, autism, and more. And Feng’s group is not even the only one in China to have created Shank3 monkeys. Another group—a collaboration primarily between researchers at Emory University and scientists in China—has done the same.

Chinese scientists’ enthusiasm for CRISPR also extends to studies of humans, which are moving much more quickly, and in some cases under less oversight, than in the West. The first studies to edit human embryos and first clinical trials for cancer therapies using CRISPR have all happened in China. [emphases mine]

Some ethical issues are also covered (from Zhang’s article),

Parents with severely epileptic children had asked him if it would be possible to study the condition in a monkey. Feng told them what he thought would be technically possible. “But I also said, ‘I’m not sure I want to generate a model like this,’” he recalled. Maybe if there were a drug to control the monkeys’ seizures, he said: “I cannot see them seizure all the time.”

But is it ethical, he continued, to let these babies die without doing anything? Is it ethical to generate thousands or millions of mutant mice for studies of brain disorders, even when you know they will not elucidate much about human conditions?

Primates should only be used if other models do not work, says Feng, and only if a clear path forward is identified. The first step in his work, he says, is to use the Shank3 monkeys to identify the changes the mutations cause in the brain. Then, researchers might use that information to find targets for drugs, which could be tested in the same monkeys. He’s talking with the Oregon National Primate Research Center about carrying out similar work in the United States. ….[Note: I have a three-part series about CRISPR and germline editing* in the US, precipitated by research coming out of Oregon, Part 1, which links to the other parts, is here.]

Zhang’s June 8, 2018 article is excellent and I highly recommend reading it.

I touched on the topic of xenotransplanttaion in a commentary on a book about the science  of the television series, Orphan Black in a January 31,2018 posting (Note: A chimera is what you use to incubate a ‘human’ organ for transplantation or, more accurately, xenotransplantation),

On the subject of chimeras, the Canadian Broadcasting Corporation (CBC) featured a January 26, 2017 article about the pig-human chimeras on its website along with a video,

The end

I am very excited to see Piccinini’s work come to Vancouver. There have been a number of wonderful art and art/science installations and discussions here but this is the first one (I believe) to tackle the emerging gene editing technologies and the issues they raise. (It also fits in rather nicely with the 200th anniversary of the publication of Mary Shelley’s Frankenstein which continues to raise issues and stimulate discussion.)

In addition to the ethical issues raised in Zhang’s article, there are some other philosophical questions:

  • what does it mean to be human
  • if we are going to edit genes to create hybrid human/animals, what are they and how do they fit into our current animal/human schema
  • are you still human if you’ve had an organ transplant where the organ was incubated in a pig

There are also going to be legal issues. In addition to any questions about legal status, there are also fights about intellectual property such as the one involving Harvard & MIT’s [Massachusetts Institute of Technology] Broad Institute vs the University of California at Berkeley (March 15, 2017 posting)..

While I’m thrilled about the Piccinini installation, it should be noted the issues raised by other artworks hosted in this version of the Biennale are important. Happily, they have been broached here in Vancouver before and I suspect this will result in more nuanced  ‘conversations’ than are possible when a ‘new’ issue is introduced.

Bravo 2018 – 2020 Vancouver Biennale!

* Germline editing is when your gene editing will affect subsequent generations as opposed to editing out a mutated gene for the lifetime of a single individual.

Art/sci and CRISPR links

This art/science posting may prove of some interest:

The connectedness of living things: an art/sci project in Saskatchewan: evolutionary biology (February 16, 2018)

A selection of my CRISPR posts:

CRISPR and editing the germline in the US (part 1 of 3): In the beginning (August 15, 2017)

NOTE: An introductory CRISPR video describing how CRISPR/Cas9 works was embedded in part1.

Why don’t you CRISPR yourself? (January 25, 2018)

Editing the genome with CRISPR ((clustered regularly interspaced short palindromic repeats)-carrying nanoparticles (January 26, 2018)

Immune to CRISPR? (April 10, 2018)

3-D integration of nanotechnologies on a single computer chip

By integrating nanomaterials , a new technique for a 3D computer chip capable of handling today’s huge amount of data has been developed. Weirdly, the first two paragraphs of a July 5, 2017 news item on Nanowerk do not convey the main point (Note: A link has been removed),

As embedded intelligence is finding its way into ever more areas of our lives, fields ranging from autonomous driving to personalized medicine are generating huge amounts of data. But just as the flood of data is reaching massive proportions, the ability of computer chips to process it into useful information is stalling.

Now, researchers at Stanford University and MIT have built a new chip to overcome this hurdle. The results are published today in the journal Nature (“Three-dimensional integration of nanotechnologies for computing and data storage on a single chip”), by lead author Max Shulaker, an assistant professor of electrical engineering and computer science at MIT. Shulaker began the work as a PhD student alongside H.-S. Philip Wong and his advisor Subhasish Mitra, professors of electrical engineering and computer science at Stanford. The team also included professors Roger Howe and Krishna Saraswat, also from Stanford.

This image helps to convey the main points,

Instead of relying on silicon-based devices, a new chip uses carbon nanotubes and resistive random-access memory (RRAM) cells. The two are built vertically over one another, making a new, dense 3-D computer architecture with interleaving layers of logic and memory. Courtesy MIT

As I hove been quite impressed with their science writing, it was a bit surprising to find that the Massachusetts Institute of Technology (MIT) had issued this news release (news item) as it didn’t follow the ‘rules’, i.e., cover as many of the journalistic questions (Who, What, Where, When, Why, and, sometimes, How) as possible in the first sentence/paragraph. This is written more in the style of a magazine article and so the details take a while to emerge, from a July 5, 2017 MIT news release, which originated the news item,

Computers today comprise different chips cobbled together. There is a chip for computing and a separate chip for data storage, and the connections between the two are limited. As applications analyze increasingly massive volumes of data, the limited rate at which data can be moved between different chips is creating a critical communication “bottleneck.” And with limited real estate on the chip, there is not enough room to place them side-by-side, even as they have been miniaturized (a phenomenon known as Moore’s Law).

To make matters worse, the underlying devices, transistors made from silicon, are no longer improving at the historic rate that they have for decades.

The new prototype chip is a radical change from today’s chips. It uses multiple nanotechnologies, together with a new computer architecture, to reverse both of these trends.

Instead of relying on silicon-based devices, the chip uses carbon nanotubes, which are sheets of 2-D graphene formed into nanocylinders, and resistive random-access memory (RRAM) cells, a type of nonvolatile memory that operates by changing the resistance of a solid dielectric material. The researchers integrated over 1 million RRAM cells and 2 million carbon nanotube field-effect transistors, making the most complex nanoelectronic system ever made with emerging nanotechnologies.

The RRAM and carbon nanotubes are built vertically over one another, making a new, dense 3-D computer architecture with interleaving layers of logic and memory. By inserting ultradense wires between these layers, this 3-D architecture promises to address the communication bottleneck.

However, such an architecture is not possible with existing silicon-based technology, according to the paper’s lead author, Max Shulaker, who is a core member of MIT’s Microsystems Technology Laboratories. “Circuits today are 2-D, since building conventional silicon transistors involves extremely high temperatures of over 1,000 degrees Celsius,” says Shulaker. “If you then build a second layer of silicon circuits on top, that high temperature will damage the bottom layer of circuits.”

The key in this work is that carbon nanotube circuits and RRAM memory can be fabricated at much lower temperatures, below 200 C. “This means they can be built up in layers without harming the circuits beneath,” Shulaker says.

This provides several simultaneous benefits for future computing systems. “The devices are better: Logic made from carbon nanotubes can be an order of magnitude more energy-efficient compared to today’s logic made from silicon, and similarly, RRAM can be denser, faster, and more energy-efficient compared to DRAM,” Wong says, referring to a conventional memory known as dynamic random-access memory.

“In addition to improved devices, 3-D integration can address another key consideration in systems: the interconnects within and between chips,” Saraswat adds.

“The new 3-D computer architecture provides dense and fine-grained integration of computating and data storage, drastically overcoming the bottleneck from moving data between chips,” Mitra says. “As a result, the chip is able to store massive amounts of data and perform on-chip processing to transform a data deluge into useful information.”

To demonstrate the potential of the technology, the researchers took advantage of the ability of carbon nanotubes to also act as sensors. On the top layer of the chip they placed over 1 million carbon nanotube-based sensors, which they used to detect and classify ambient gases.

Due to the layering of sensing, data storage, and computing, the chip was able to measure each of the sensors in parallel, and then write directly into its memory, generating huge bandwidth, Shulaker says.

Three-dimensional integration is the most promising approach to continue the technology scaling path set forth by Moore’s laws, allowing an increasing number of devices to be integrated per unit volume, according to Jan Rabaey, a professor of electrical engineering and computer science at the University of California at Berkeley, who was not involved in the research.

“It leads to a fundamentally different perspective on computing architectures, enabling an intimate interweaving of memory and logic,” Rabaey says. “These structures may be particularly suited for alternative learning-based computational paradigms such as brain-inspired systems and deep neural nets, and the approach presented by the authors is definitely a great first step in that direction.”

“One big advantage of our demonstration is that it is compatible with today’s silicon infrastructure, both in terms of fabrication and design,” says Howe.

“The fact that this strategy is both CMOS [complementary metal-oxide-semiconductor] compatible and viable for a variety of applications suggests that it is a significant step in the continued advancement of Moore’s Law,” says Ken Hansen, president and CEO of the Semiconductor Research Corporation, which supported the research. “To sustain the promise of Moore’s Law economics, innovative heterogeneous approaches are required as dimensional scaling is no longer sufficient. This pioneering work embodies that philosophy.”

The team is working to improve the underlying nanotechnologies, while exploring the new 3-D computer architecture. For Shulaker, the next step is working with Massachusetts-based semiconductor company Analog Devices to develop new versions of the system that take advantage of its ability to carry out sensing and data processing on the same chip.

So, for example, the devices could be used to detect signs of disease by sensing particular compounds in a patient’s breath, says Shulaker.

“The technology could not only improve traditional computing, but it also opens up a whole new range of applications that we can target,” he says. “My students are now investigating how we can produce chips that do more than just computing.”

“This demonstration of the 3-D integration of sensors, memory, and logic is an exceptionally innovative development that leverages current CMOS technology with the new capabilities of carbon nanotube field–effect transistors,” says Sam Fuller, CTO emeritus of Analog Devices, who was not involved in the research. “This has the potential to be the platform for many revolutionary applications in the future.”

This work was funded by the Defense Advanced Research Projects Agency [DARPA], the National Science Foundation, Semiconductor Research Corporation, STARnet SONIC, and member companies of the Stanford SystemX Alliance.

Here’s a link to and a citation for the paper,

Three-dimensional integration of nanotechnologies for computing and data storage on a single chip by Max M. Shulaker, Gage Hills, Rebecca S. Park, Roger T. Howe, Krishna Saraswat, H.-S. Philip Wong, & Subhasish Mitra. Nature 547, 74–78 (06 July 2017) doi:10.1038/nature22994 Published online 05 July 2017

This paper is behind a paywall.

Shades of the Nokia Morph: a smartphone than conforms to your wrist

A March 16, 2017 news item on Nanowerk brought back some memories for me,

Some day, your smartphone might completely conform to your wrist, and when it does, it might be covered in pure gold, thanks to researchers at Missouri University of Science and Technology.

Nokia, a Finnish telecommunications company, was promoting its idea for a smartphone ‘and more’ that could be worn around your wrist in a concept called the Morph. It was introduced in 2008 at the Museum of Modern Art in New York City (see my March 20, 2010 posting for one of my last updates on this moribund project). Here’s Nokia’s Morph video (almost 6 mins.),

Getting back to the present day, here’s what the Missouri researchers are working on,

An example of a gold foil peeled from single crystal silicon. Reprinted with permission from Naveen Mahenderkar et al., Science [355]:[1203] (2017)

A March 16, 2017 Missouri University of Science and Technology news release, by Greg Katski, which originated the news item, provides more details about this Missouri version (Note: A link has been removed),

Writing in the March 17 [2017] issue of the journal Science, the S&T researchers say they have developed a way to “grow” thin layers of gold on single crystal wafers of silicon, remove the gold foils, and use them as substrates on which to grow other electronic materials. The research team’s discovery could revolutionize wearable or “flexible” technology research, greatly improving the versatility of such electronics in the future.

According to lead researcher Jay A. Switzer, the majority of research into wearable technology has been done using polymer substrates, or substrates made up of multiple crystals. “And then they put some typically organic semiconductor on there that ends up being flexible, but you lose the order that (silicon) has,” says Switzer, Donald L. Castleman/FCR Endowed Professor of Discovery in Chemistry at S&T.

Because the polymer substrates are made up of multiple crystals, they have what are called grain boundaries, says Switzer. These grain boundaries can greatly limit the performance of an electronic device.

“Say you’re making a solar cell or an LED,” he says. “In a semiconductor, you have electrons and you have holes, which are the opposite of electrons. They can combine at grain boundaries and give off heat. And then you end up losing the light that you get out of an LED, or the current or voltage that you might get out of a solar cell.”

Most electronics on the market are made of silicon because it’s “relatively cheap, but also highly ordered,” Switzer says.

“99.99 percent of electronics are made out of silicon, and there’s a reason – it works great,” he says. “It’s a single crystal, and the atoms are perfectly aligned. But, when you have a single crystal like that, typically, it’s not flexible.”

By starting with single crystal silicon and growing gold foils on it, Switzer is able to keep the high order of silicon on the foil. But because the foil is gold, it’s also highly durable and flexible.

“We bent it 4,000 times, and basically the resistance didn’t change,” he says.

The gold foils are also essentially transparent because they are so thin. According to Switzer, his team has peeled foils as thin as seven nanometers.

Switzer says the challenge his research team faced was not in growing gold on the single crystal silicon, but getting it to peel off as such a thin layer of foil. Gold typically bonds very well to silicon.

“So we came up with this trick where we could photo-electrochemically oxidize the silicon,” Switzer says. “And the gold just slides off.”

Photoelectrochemical oxidation is the process by which light enables a semiconductor material, in this case silicon, to promote a catalytic oxidation reaction.

Switzer says thousands of gold foils—or foils of any number of other metals—can be made from a single crystal wafer of silicon.

The research team’s discovery can be considered a “happy accident.” Switzer says they were looking for a cheap way to make single crystals when they discovered this process.

“This is something that I think a lot of people who are interested in working with highly ordered materials like single crystals would appreciate making really easily,” he says. “Besides making flexible devices, it’s just going to open up a field for anybody who wants to work with single crystals.”

Here’s a link to and a citation for the paper,

Epitaxial lift-off of electrodeposited single-crystal gold foils for flexible electronics by Naveen K. Mahenderkar, Qingzhi Chen, Ying-Chau Liu, Alexander R. Duchild, Seth Hofheins, Eric Chason, Jay A. Switzer. Science  17 Mar 2017: Vol. 355, Issue 6330, pp. 1203-1206 DOI: 10.1126/science.aam5830

This paper is behind a paywall.

Nanomedicine and an enhanced uptake of nanoparticles

It’s nice to know that a step forward has been taken with regard to improving uptake in  nanoparticle-based drug delivery (see my April 27, 2016 posting titled: How many nanoparticle-based drugs does it take to kill a cancer tumour? More than 1% for insight into the difficulties of f nanoparticle-based drug delivery systems).

Here’s the latest move forward in a March 8, 2017 news item on Nanowerk (Note: A link has been removed),

Nanotechnology has become a growing part of medical research in recent years, with scientists feverishly working to see if tiny particles could revolutionize the world of drug delivery.

But many questions remain about how to effectively transport those particles and associated drugs to cells.
In an article published today in Scientific Reports (“Enhanced cellular uptake of size-separated lipophilic silicon nanoparticles”), FSU Associate Professor of Biological Science Steven Lenhert takes a step forward in the understanding of nanoparticles and how they can best be used to deliver drugs.

After conducting a series of experiments, Lenhert and his colleagues found that it may be possible to boost the efficacy of medicine entering target cells via a nanoparticle.

A March 8, 2017 Florida State University news release by Kathleen Haughney, which originated the news item, provides more detail about the research (an international collaboration involving the University of Toronto [Canada] and the Karlsruhe Institute of Technology [Germany]),

“We can enhance how cells take them up and make more drugs more potent,” Lenhert said.

Initially, Lenhert and his colleagues from the University of Toronto and the Karlsruhe Institute of Technology  wanted to see what happened when they encapsulated silicon nanoparticles in liposomes — or small spherical sacs of molecules — and delivered them to HeLa cells, a standard cancer cell model.

The initial goal was to test the toxicity of silicon-based nanoparticles and get a better understanding of its biological activity.

Silicon is a non-toxic substance and has well-known optical properties that allow their nanostructures to appear fluorescent under an infrared camera, where tissue would be nearly transparent. Scientists believe it has enormous potential as a delivery agent for drugs as well as in medical imaging.

But there are still questions about how silicon behaves at such a small size.

“Nanoparticles change properties as they get smaller, so scientists want to understand the biological activity,” Lenhert said. “For example, how does shape and size affect toxicity?”

Scientists found that 10 out of 18 types of the particles, ranging from 1.5 nanometers to 6 nanometers, were significantly more toxic than crude mixtures of the material.

At first, scientists believed this could be a setback, but they then discovered the reason for the toxicity levels. The more toxic fragments also had enhanced cellular uptake.

That information is more valuable long term, Lenhert said, because it means they could potentially alter nanoparticles to enhance the potency of a given therapeutic.

The work also paves the way for researchers to screen libraries of nanoparticles to see how cells react.

“This is an essential step toward the discovery of novel nanotechnology based therapeutics,” Lenhert said. “There’s big potential here for new therapeutics, but we need to be able to test everything first.”

Here’s a link to and a citation for the paper,

Enhanced cellular uptake of size-separated lipophilic silicon nanoparticles by Aubrey E. Kusi-Appiah, Melanie L. Mastronardi, Chenxi Qian, Kenneth K. Chen, Lida Ghazanfari, Plengchart Prommapan, Christian Kübel, Geoffrey A. Ozin, & Steven Lenhert. Scientific Reports 7, Article number: 43731 (2017) doi:10.1038/srep43731 Published online: 08 March 2017

This paper is open access.

Phagocytosis for a bioelectronic future

The process by which a cell engulfs matter is known as phagocytosis. One of the best known examples of failed phagocytosis is that of asbestos fibres in the lungs where lung cells have attempted to engulf a fibre that’s just too big and ends up piercing the cell. When enough of the cells are pierced, the person is diagnosed with mesothelioma.

This particular example of phagocytosis is a happier one according to a Dec. 16, 2016 article by Meghan Rosen for ScienceNews,

Human cells can snack on silicon.

Cells grown in the lab devour nano-sized wires of silicon through an engulfing process known as phagocytosis, scientists report December 16 in Science Advances.

Silicon-infused cells could merge electronics with biology, says John Zimmerman, a biophysicist now at Harvard University. “It’s still very early days,” he adds, but “the idea is to get traditional electronic devices working inside of cells.” Such hybrid devices could one day help control cellular behavior, or even replace electronics used for deep brain stimulation, he says.

Scientists have been trying to load electronic parts inside cells for years. One way is to zap holes in cells with electricity, which lets big stuff, like silicon nanowires linked to bulky materials, slip in. Zimmerman, then at the University of Chicago, and colleagues were looking for a simpler technique, something that would let tiny nanowires in easily and could potentially allow them to travel through a person’s bloodstream — like a drug.

A Dec. 22, 2016 University of Chicago news release by Matt Wood provides more detail,

“You can treat it as a non-genetic, synthetic biology platform,” said Bozhi Tian, PhD, assistant professor of chemistry and senior author of the new study. “Traditionally in biology we use genetic engineering and modify genetic parts. Now we can use silicon parts, and silicon can be internalized. You can target those silicon parts to specific parts of the cell and modulate that behavior with light.”

In the new study, Tian and his team show how cells consume or internalize the nanowires through phagocytosis, the same process they use to engulf and ingest nutrients and other particles in their environment. The nanowires are simply added to cell media, the liquid solution the cells live in, the same way you might administer a drug, and the cells take it from there. Eventually, the goal would be to inject them into the bloodstream or package them into a pill.

Once inside, the nanowires can interact directly with individual parts of the cell, organelles like the mitochondria, nucleus and cytoskeletal filaments. Researchers can then stimulate the nanowires with light to see how individual components of the cell respond, or even change the behavior of the cell. They can last up to two weeks inside the cell before biodegrading.

Seeing how individual parts of a cell respond to stimulation could give researchers insight into how medical treatments that use electrical stimulation work at a more detailed level. For instance, deep brain stimulation helps treat tremors from movement disorders like Parkinson’s disease by sending electrical signals to areas of the brain. Doctors know it works at the level of tissues and brain structures, but seeing how individual components of nerve cells react to these signals could help fine tune and improve the treatment.

The experiments in the study used umbilical vascular endothelial cells, which make up blood vessel linings in the umbilical cord. These cells readily took up the nanowires, but others, like cardiac muscle cells, did not. Knowing that some cells consume the wires and some don’t could also prove useful in experimental settings and give researchers more ways to target specific cell types.

Tian and his team manufactures the nanowires in their lab with a chemical vapor deposition system that grows the silicon structures to different specifications. They can adjust size, shape, and electrical properties as needed, or even add defects on purpose for testing. They can also make wires with porous surfaces that could deliver drugs or genetic material to the cells. The process gives them a variety of ways to manipulate the properties of the nanowires for research.

Seeing how individual parts of a cell respond to stimulation could give researchers insight into how medical treatments that use electrical stimulation work at a more detailed level. For instance, deep brain stimulation helps treat tremors from movement disorders like Parkinson’s disease by sending electrical signals to areas of the brain. Doctors know it works at the level of tissues and brain structures, but seeing how individual components of nerve cells react to these signals could help fine tune and improve the treatment.

The experiments in the study used umbilical vascular endothelial cells, which make up blood vessel linings in the umbilical cord. These cells readily took up the nanowires, but others, like cardiac muscle cells, did not. Knowing that some cells consume the wires and some don’t could also prove useful in experimental settings and give researchers more ways to target specific cell types.

Tian and his team manufactures the nanowires in their lab with a chemical vapor deposition system that grows the silicon structures to different specifications. They can adjust size, shape, and electrical properties as needed, or even add defects on purpose for testing. They can also make wires with porous surfaces that could deliver drugs or genetic material to the cells. The process gives them a variety of ways to manipulate the properties of the nanowires for research.

Here’s a link to and a citation for the paper,

Cellular uptake and dynamics of unlabeled freestanding silicon nanowires by John F. Zimmerman, Ramya Parameswaran, Graeme Murray, Yucai Wang, Michael Burke, and Bozhi Tian. Science Advances  16 Dec 2016: Vol. 2, no. 12, e1601039 DOI: 10.1126/sciadv.1601039

This paper appears to be open access.

Steering a synthetic nanorobot using light

This news comes from the University of Hong Kong. A Nov. 8, 2016 news item on Nanowerk throws some light on the matter (Note: A link has been removed),

A team of researchers led by Dr Jinyao Tang of the Department of Chemistry, the University of Hong Kong, has developed the world’s first light-seeking synthetic Nano robot. With size comparable to a blood cell, those tiny robots have the potential to be injected into patients’ bodies, helping surgeons to remove tumors and enabling more precise engineering of targeted medications. The findings have been published in October [2016] earlier in leading scientific journal Nature Nanotechnology (“Programmable artificial phototactic microswimmer”).

An Oct. 24, 2016 University of Hong Kong press release (also on EurekAlert), which originated the news item, expands on the theme,

It has been a dream in science fiction for decades that tiny robots can fundamentally change our daily life. The famous science fiction  movie “Fantastic  Voyage” is a very good example, with a group of scientists driving their miniaturized nano-submarine inside human body to repair a damaged brain. In the film “Terminator  2,” billions of nanorobots were assembled into the amazing shapeshifting body: the T-1000. In the real world, it is quite challenging to make and design a sophisticated nanorobot with advanced functions.

The Nobel Prize in Chemistry 2016 was awarded to three scientists for “the design and synthesis of molecular machines.” They developed a set of mechanical components at molecular scale which may be  assembled into  more complicated nanomachines  to  manipulate single  molecule such as DNA or proteins in the future. The development of tiny nanoscale machines for biomedical applications has been a major trend of scientific research in recent years. Any breakthroughs will potentially open the door to new knowledge and treatments of diseases and development of new drugs.

One difficulty in nanorobot design is to make these nanostructures sense and respond to the environment. Given each nanorobot is only a few micrometer in size which is ~50 times smaller than the diameter of a human hair, it  is very difficult  to  squeeze  normal electronic sensors and circuits into  nanorobots with reasonable price. Currently, the only method to remotely control nanorobots is to  incorporate tiny magnetic inside the nanorobot and guide the motion via external magnetic field.

The  nanorobot developed by Dr Tang’s team use light as the propelling  force, and is the first research team globally to explore the light-guided nanorobots and demonstrated its feasibility and effectiveness. In their paper published in Nature  Nanotechnology, Dr Tang’s team  demonstrated  the  unprecedented ability of these light-controlled nanorobots as they are “dancing”  or even spell a word under light control. With a novel  nanotree structure, the nanorobots can respond to the light shining on it like  moths  being drawn to flames. Dr Tang described the motions as if “they can “see” the light and drive itself towards it”.

The team gained inspiration from natural green algae
for the nanorobot design. In nature, some green algae have evolved  with  the  ability  of  sensing  light  around  it.  Even just a single cell, these green  algae can sense the intensity of light and swim  towards the light source for photosynthesis. Dr  Jinyao  Tang’s team successfully developed the nanorobots after over three years’ efforts. With a novel nanotree structure, they are composed of two  common and low-price semiconductor materials: silicon  and titanium oxide. During  the  synthesis, silicon  and titanium oxide are shaped into nanowire and then further arranged into a tiny nanotree heterostructure.

Dr Tang said: “Although the current nanorobot cannot be used for disease treatment yet, we are working on the next generation nanorobotic system which is more efficient and biocompatible.”

“Light is a more effective option to communicate between microscopic world and macroscopic world. We can conceive that more complicated instructions can be sent to nanorobots which provide scientists with a new tool to further develop more functions into nanorobot and get us one step closer to daily life applications,” he added.

Here’s a link to and a citation for the paper,

Programmable artificial phototactic microswimmer by Baohu Dai, Jizhuang Wang, Ze Xiong, Xiaojun Zhan, Wei Dai, Chien-Cheng Li, Shien-Ping Feng, & Jinyao Tang.  Nature Nanotechnology (2016)  doi:10.1038/nnano.2016.187 Published online 17 October 2016

So, this ‘bot’ seems to be a microbot or microrobot with some nanoscale features. In any event, the paper is behind a paywall.

US white paper on neuromorphic computing (or the nanotechnology-inspired Grand Challenge for future computing)

The US has embarked on a number of what is called “Grand Challenges.” I first came across the concept when reading about the Bill and Melinda Gates (of Microsoft fame) Foundation. I gather these challenges are intended to provide funding for research that advances bold visions.

There is the US National Strategic Computing Initiative established on July 29, 2015 and its first anniversary results were announced one year to the day later. Within that initiative a nanotechnology-inspired Grand Challenge for Future Computing was issued and, according to a July 29, 2016 news item on Nanowerk, a white paper on the topic has been issued (Note: A link has been removed),

Today [July 29, 2016), Federal agencies participating in the National Nanotechnology Initiative (NNI) released a white paper (pdf) describing the collective Federal vision for the emerging and innovative solutions needed to realize the Nanotechnology-Inspired Grand Challenge for Future Computing.

The grand challenge, announced on October 20, 2015, is to “create a new type of computer that can proactively interpret and learn from data, solve unfamiliar problems using what it has learned, and operate with the energy efficiency of the human brain.” The white paper describes the technical priorities shared by the agencies, highlights the challenges and opportunities associated with these priorities, and presents a guiding vision for the research and development (R&D) needed to achieve key technical goals. By coordinating and collaborating across multiple levels of government, industry, academia, and nonprofit organizations, the nanotechnology and computer science communities can look beyond the decades-old approach to computing based on the von Neumann architecture and chart a new path that will continue the rapid pace of innovation beyond the next decade.

A July 29, 2016 US National Nanotechnology Coordination Office news release, which originated the news item, further and succinctly describes the contents of the paper,

“Materials and devices for computing have been and will continue to be a key application domain in the field of nanotechnology. As evident by the R&D topics highlighted in the white paper, this challenge will require the convergence of nanotechnology, neuroscience, and computer science to create a whole new paradigm for low-power computing with revolutionary, brain-like capabilities,” said Dr. Michael Meador, Director of the National Nanotechnology Coordination Office. …

The white paper was produced as a collaboration by technical staff at the Department of Energy, the National Science Foundation, the Department of Defense, the National Institute of Standards and Technology, and the Intelligence Community. …

The white paper titled “A Federal Vision for Future Computing: A Nanotechnology-Inspired Grand Challenge” is 15 pp. and it offers tidbits such as this (Note: Footnotes not included),

A new materials base may be needed for future electronic hardware. While most of today’s electronics use silicon, this approach is unsustainable if billions of disposable and short-lived sensor nodes are needed for the coming Internet-of-Things (IoT). To what extent can the materials base for the implementation of future information technology (IT) components and systems support sustainability through recycling and bio-degradability? More sustainable materials, such as compostable or biodegradable systems (polymers, paper, etc.) that can be recycled or reused,  may play an important role. The potential role for such alternative materials in the fabrication of integrated systems needs to be explored as well. [p. 5]

The basic architecture of computers today is essentially the same as those built in the 1940s—the von Neumann architecture—with separate compute, high-speed memory, and high-density storage components that are electronically interconnected. However, it is well known that continued performance increases using this architecture are not feasible in the long term, with power density constraints being one of the fundamental roadblocks.7 Further advances in the current approach using multiple cores, chip multiprocessors, and associated architectures are plagued by challenges in software and programming models. Thus,  research and development is required in radically new and different computing architectures involving processors, memory, input-output devices, and how they behave and are interconnected. [p. 7]

Neuroscience research suggests that the brain is a complex, high-performance computing system with low energy consumption and incredible parallelism. A highly plastic and flexible organ, the human brain is able to grow new neurons, synapses, and connections to cope with an ever-changing environment. Energy efficiency, growth, and flexibility occur at all scales, from molecular to cellular, and allow the brain, from early to late stage, to never stop learning and to act with proactive intelligence in both familiar and novel situations. Understanding how these mechanisms work and cooperate within and across scales has the potential to offer tremendous technical insights and novel engineering frameworks for materials, devices, and systems seeking to perform efficient and autonomous computing. This research focus area is the most synergistic with the national BRAIN Initiative. However, unlike the BRAIN Initiative, where the goal is to map the network connectivity of the brain, the objective here is to understand the nature, methods, and mechanisms for computation,  and how the brain performs some of its tasks. Even within this broad paradigm,  one can loosely distinguish between neuromorphic computing and artificial neural network (ANN) approaches. The goal of neuromorphic computing is oriented towards a hardware approach to reverse engineering the computational architecture of the brain. On the other hand, ANNs include algorithmic approaches arising from machinelearning,  which in turn could leverage advancements and understanding in neuroscience as well as novel cognitive, mathematical, and statistical techniques. Indeed, the ultimate intelligent systems may as well be the result of merging existing ANN (e.g., deep learning) and bio-inspired techniques. [p. 8]

As government documents go, this is quite readable.

For anyone interested in learning more about the future federal plans for computing in the US, there is a July 29, 2016 posting on the White House blog celebrating the first year of the US National Strategic Computing Initiative Strategic Plan (29 pp. PDF; awkward but that is the title).

Unleashing graphene electronics potential with a trio of 2D nanomaterials

Graphene has excited a great deal of interest, especially with regard to its application in the field of electronics. However, it seems that graphene may need a little help from its friends, tantalum sulfide and boron nitride, according to a July 6, 2016 news item on ScienceDaily,

Graphene has emerged as one of the most promising two-dimensional crystals, but the future of electronics may include two other nanomaterials, according to a new study by researchers at the University of California, Riverside and the University of Georgia.

In research published Monday (July 4 [2016]) in the journal Nature Nanotechnology, the researchers described the integration of three very different two-dimensional (2D) materials to yield a simple, compact, and fast voltage-controlled oscillator (VCO) device. A VCO is an electronic oscillator whose oscillation frequency is controlled by a voltage input.

Titled “An integrated Tantalum Sulfide–Boron Nitride–Graphene Oscillator: A Charge-Density-Wave Device Operating at Room Temperature,” the paper describes the development of the first useful device that exploits the potential of charge-density waves to modulate an electrical current through a 2D material. The new technology could become an ultralow power alternative to conventional silicon-based devices, which are used in thousands of applications from computers to clocks to radios. The thin, flexible nature of the device would make it ideal for use in wearable technologies.

A July 5, 2016 University of California at Riverside (UCR) news release (also on EurekAlert) by Sarah Nightingale, which originated the news item, expands on the theme,

Graphene, a single layer of carbon atoms that exhibits exceptional electrical and thermal conductivities, shows promise as a successor to silicon-based transistors. However, its application has been limited by its inability to function as a semiconductor, which is critical for the ‘on-off’ switching operations performed by electronic components.

To overcome this shortfall, the researchers turned to another 2D nanomaterial, Tantalum Sulfide (TaS2). They showed that voltage-induced changes in the atomic structure of the ‘1T prototype’ of TaS2 enable it to function as an electrical switch at room temperature–a requirement for practical applications.

“There are many charge-density wave materials that have interesting electrical switching properties. However, most of them reveal these properties at very low temperature only. The particular polytype of TaS2 that we used can have abrupt changes in resistance above room temperature. That made a crucial difference,” said Alexander Balandin, UC presidential chair professor of electrical and computer engineering in UCR’s Bourns College of Engineering, who led the research team.

To protect the TaS2 from environmental damage, the researchers coated it with another 2D material, hexagonal boron nitrate, to prevent oxidation. By pairing the boron nitride-capped TaS2 with graphene, the team constructed a three-layer VCO that could pave the way for post-silicon electronics. In the proposed design, graphene functions as an integrated tunable load resistor, which enables precise voltage control of the current and VCO frequency. The prototype UCR devices operated at MHz frequency used in radios, and the extremely fast physical processes that define the device functionality allow for the operation frequency to increase all the way to THz.

Balandin said the integrated system is the first example of a functional voltage-controlled oscillator device comprising 2D materials that operates at room temperature.

“It is difficult to compete with silicon, which has been used and improved for the past 50 years. However, we believe our device shows a unique integration of three very different 2D materials, which utilizes the intrinsic properties of each of these materials. The device can potentially become a low-power alternative to conventional silicon technologies in many different applications,” Balandin said.

The electronic function of graphene envisioned in the proposed 2D device overcomes the problem associated with the absence of the energy band gap, which so far prevented graphene’s use as the transistor channel material. The extremely high thermal conductivity of graphene comes as an additional benefit in the device structure, by facilitating heat removal. The unique heat conduction properties of graphene were experimentally discovered and theoretically explained in 2008 by Balandin’s group at UCR. The Materials Research Society recognized this groundbreaking achievement by awarding Balandin the MRS Medal in 2013.

The Balandin group also demonstrated the first integrated graphene heat spreaders for high-power transistors and light-emitting diodes. “In those applications, graphene was used exclusively as heat conducting material. Its thermal conductivity was the main property. In the present device, we utilize both electrical and thermal conductivity of graphene,” Balandin added.

Here’s a link to and a citation for the paper,

A charge-density-wave oscillator based on an integrated tantalum disulfide–boron nitride–graphene device operating at room temperature by Guanxiong Liu, Bishwajit Debnath, Timothy R. Pope, Tina T. Salguero, Roger K. Lake, & Alexander A. Balandin. Nature Nanotechnology (2016) doi:10.1038/nnano.2016.108 Published online 04 July 2016

This paper is behind a paywall.

IBM, the Cognitive Era, and carbon nanotube electronics

IBM has a storied position in the field of nanotechnology due to the scanning tunneling microscope developed in the company’s laboratories. It was a Nobel Prize-winning breakthough which provided the impetus for nanotechnology applied research. Now, an Oct. 1, 2015 news item on Nanowerk trumpets another IBM breakthrough,

IBM Research today [Oct. 1, 2015] announced a major engineering breakthrough that could accelerate carbon nanotubes replacing silicon transistors to power future computing technologies.

IBM scientists demonstrated a new way to shrink transistor contacts without reducing performance of carbon nanotube devices, opening a pathway to dramatically faster, smaller and more powerful computer chips beyond the capabilities of traditional semiconductors.

While the Oct. 1, 2015 IBM news release, which originated the news item, does go on at length there’s not much technical detail (see the second to last paragraph in the excerpt for the little they do include) about the research breakthrough (Note: Links have been removed),

IBM’s breakthrough overcomes a major hurdle that silicon and any semiconductor transistor technologies face when scaling down. In any transistor, two things scale: the channel and its two contacts. As devices become smaller, increased contact resistance for carbon nanotubes has hindered performance gains until now. These results could overcome contact resistance challenges all the way to the 1.8 nanometer node – four technology generations away. [emphasis mine]

Carbon nanotube chips could greatly improve the capabilities of high performance computers, enabling Big Data to be analyzed faster, increasing the power and battery life of mobile devices and the Internet of Things, and allowing cloud data centers to deliver services more efficiently and economically.

Silicon transistors, tiny switches that carry information on a chip, have been made smaller year after year, but they are approaching a point of physical limitation. With Moore’s Law running out of steam, shrinking the size of the transistor – including the channels and contacts – without compromising performance has been a vexing challenge troubling researchers for decades.

IBM has previously shown that carbon nanotube transistors can operate as excellent switches at channel dimensions of less than ten nanometers – the equivalent to 10,000 times thinner than a strand of human hair and less than half the size of today’s leading silicon technology. IBM’s new contact approach overcomes the other major hurdle in incorporating carbon nanotubes into semiconductor devices, which could result in smaller chips with greater performance and lower power consumption.

Earlier this summer, IBM unveiled the first 7 nanometer node silicon test chip [emphasis mine], pushing the limits of silicon technologies and ensuring further innovations for IBM Systems and the IT industry. By advancing research of carbon nanotubes to replace traditional silicon devices, IBM is paving the way for a post-silicon future and delivering on its $3 billion chip R&D investment announced in July 2014.

“These chip innovations are necessary to meet the emerging demands of cloud computing, Internet of Things and Big Data systems,” said Dario Gil, vice president of Science & Technology at IBM Research. “As silicon technology nears its physical limits, new materials, devices and circuit architectures must be ready to deliver the advanced technologies that will be required by the Cognitive Computing era. This breakthrough shows that computer chips made of carbon nanotubes will be able to power systems of the future sooner than the industry expected.”

A New Contact for Carbon Nanotubes

Carbon nanotubes represent a new class of semiconductor materials that consist of single atomic sheets of carbon rolled up into a tube. The carbon nanotubes form the core of a transistor device whose superior electrical properties promise several generations of technology scaling beyond the physical limits of silicon.

Electrons in carbon transistors can move more easily than in silicon-based devices, and the ultra-thin body of carbon nanotubes provide additional advantages at the atomic scale. Inside a chip, contacts are the valves that control the flow of electrons from metal into the channels of a semiconductor. As transistors shrink in size, electrical resistance increases within the contacts, which impedes performance. Until now, decreasing the size of the contacts on a device caused a commensurate drop in performance – a challenge facing both silicon and carbon nanotube transistor technologies.

IBM researchers had to forego traditional contact schemes and invented a metallurgical process akin to microscopic welding that chemically binds the metal atoms to the carbon atoms at the ends of nanotubes. This ‘end-bonded contact scheme’ allows the contacts to be shrunken down to below 10 nanometers without deteriorating performance of the carbon nanotube devices.

“For any advanced transistor technology, the increase in contact resistance due to the decrease in the size of transistors becomes a major performance bottleneck,” Gil added. “Our novel approach is to make the contact from the end of the carbon nanotube, which we show does not degrade device performance. This brings us a step closer to the goal of a carbon nanotube technology within the decade.”

Every once in a while, the size gets to me and a 1.8nm node is amazing. As for IBM’s 7nm chip, which was previewed this summer, there’s more about that in my July 15, 2015 posting.

Here’s a link to and a citation for the IBM paper,

End-bonded contacts for carbon nanotube transistors with low, size-independent resistance by Qing Cao, Shu-Jen Han, Jerry Tersoff, Aaron D. Franklin†, Yu Zhu, Zhen Zhang‡, George S. Tulevski, Jianshi Tang, and Wilfried Haensch. Science 2 October 2015: Vol. 350 no. 6256 pp. 68-72 DOI: 10.1126/science.aac8006

This paper is behind a paywall.